Switching contact



May 25, 1943.

' R. c. MATHES SWITCHING CONTACT Filed March 15, 1941 2 Sheets-Sheet lATTORNEY y 25, 1 R. c. MATHES 2,319,937

SWITCHING CONTACT Filed March 15, 1941 2 Sheets-Sheet 2 FIG. 3

lNl/ENTOR R C. MATHES' ATTORNEY.

Patented May 25, 1943 1 7 2,319,937 SWITCHING GONTACT Robert G. Mathes,Maplewood, N. J., assignor to Bell Telephone Laboratories,

Incorporated,

New York, N. Y., a corporation of New York Application March 15, 1941,Serial No. 383,563

10 Claims. (Cl. 179-430) This invention relates to signaling systems andparticularly to the operation of switching'contacts for signaling bycontrol of an electrical circuit.

The object of the invention is to improve the construction andfunctioning of such apparatus by insuring the positive operation of theswitching contacts; eliminating moving mechanical parts and using sealedcontacts which are protected against corrosion and the other ills ofopen air contacts.

The invention may generally be defined as magnetic switching since it isthe object of the invention to operate the electrical contacts forcontrolling the signaling path by performing a signaling operation whichprimarily changes a magnetic circuit. Through the use of magneticallyoperated contact devices such as the sealed reed and 'mercury contacts,among others, the control of the signaling circuit may be carried outunder more favorable conditions than heretofore.

When applied to telephone apparatus the invention may be defined asrelating to magnetic dialing and magnetic switchhook operation sincewhile the signals in existing systems are created by the direct actionof mechanicalmeans for the dialing and switchhook operations in themethod proposed the intervening control is purely magnetic.

Generally stated a magnetic circuit is provided in the support or cradlefor the telephone, such circuit including a set of magnetically operatedswitching contacts. Through the use of a magnetic element in thetelephone the field of a permanent magnet in the said magnetic circuitis sufficiently diverted from the said magnetically operated contacts toallow them to release when the telephone is placed on its cradle. Adialing device comprising means to periodically and magnetically shuntthat part of the said magnetic circuit aliected by the magnetic elementin the telephone is provided. When the telephone is on its cradle thisdialing device is ineffective since th magnetic contacts have alreadybeen released. However, when the telephone has been removed from itscradle the contacts are in their operated positions and then the dialingdevice becomes effective to periodically sufficiently divert the fieldof the permanent magnet from such contacts whereupon they operate toperiodically open and close the line circuit, since in this case theline circuit is affected by both the switchhook and dialing operations.

In one form of the invention a simple magnetic circuit operating inresponse to the movement of a dial is provided. In another form a magnetic circuit responsive to both switchhook and dialing operations isemployed. In still another form a magnetic circuit is employed in awellknown type of signal transmitter by which impulses of differentlength and in code are transmitted. The invention may be further appliedto other types of signal transmitters.

The magnetically operated contacts may be of any well-known form, thoughherein sealed contacts are shown as being preferable to meremagnetically movable open contacts. Since applicant does not claim anyparticular type of contact device it may be noted that among manyothers, the contacts of the following examples of the prior art may beusefully employed.

Cox, 2,207,506, July 9, 1940; Leece et al., 2,029,- 266, Jan. 29, 1936;Ellwood et al., 2,187, 115, Jan. 16, 1940; Harrison et al., Serial No.302,526, filed Nov. 2, 1939.

A feature of the invention is a magnetic circuit including a permanentmagnet normally arranged to operate a set of magnetically responsivecircuit contacts in combination with signaling means including amagnetic element constructed and arranged upon each signaling operationto sufficiently divert the field of said permanent magnet from saidcontacts to allow them to release.

Another feature of the invention is a combined magnetic circuit forperforming a plurality of signaling operations whereby a first signalingoperation is automatically prevented until a second signaling operationhas been performed. Specifically a dialing operation is automaticallyprevented until a switchhook operation has been performed.

Another feature of the invention is the use of a movable element as partof a magnetic circit which will so affect the said magnetic circuit asto cause a response by magnetically operated circuit contacts, eitherperiodically or according to a predetermined pattern of equally orunequally timed operations.

Other features will appear in the following description.

The drawings consist of two sheets, one having two figures representingin skeletonized form a telephone instrument comprising a handset, acradle therefor, a dial and a magnetic circuit for operating a set ofcontact elements, and another sheet having two figures representing indiagrammatic form a signal transmitter operated by a twist of thehandle, such as the well-known messenger call boxes.

Fig. 1 shows an arrangement in which the magnetic circuit is effectedboth by the movement of the handset and the movement of the dial;

Fig. 2 shows a similar arrangement in which the magnetic circuit iseffected only by the dial;

Fig. 3 is a diagrammatic showing of a signal transmitter which will senda train of pulses of unequal length; and

Fig. 4 is an end view of the essential elements of the device of Fig. 3.

In Figs. 1 and 2 a telephone handset I and the cradle 2 therefor areshown in broken line outlines. In both figures, also, a dial 3 isindicated together with a castellated armature 4 moved by the dial. Theterm castellated armature used herein and in the appended claims will be'understood as a spoked member of the general design and appearance ofthe member 4, the term castellated being intended to be generic innature and to cover variations in this device including one in which theends of the spokes might be turned up at a position .normal to the planeof the member and thus plainly resemble the generally understood contourof the battlement of a castle.

In Fig. I aipair' of soft iron elements 5 and 6 are indicated as mountedwithin the cradle 2. A permanent magnet I is mounted in the cradle withair gaps between its ends and the soft iron elements Sand 6. A set ofcontacts 8 is mounted between the soft iron elements 5 and 6 in aposition parallel to the permanent magnet I; This contact set is? hererepresented as a sealed reed contact device of the type developed byEllwood and shown in the Ellwood patent hereinbefore noted. It consistsof aiglass tube in which two magnetic reeds are placed in such aposition that whena magnetic field is passing therethrough, these reedswill be attracted to each other and will make an electrical contacttherebetween. It will be understood, of course; that the contact deviceV8-is representative and may represent a plurality of such contacts ifthe circuit in which they are used calls for a plurality of circuits tobe opened and closed. 'Another soft iron element 9 ismounted'withinthehandset I in such a position'that when the handset l is resting on itscradle as shown, it will sufficiently divert the field of the permanentmagnet 1 through the upper 'portionsofthe soft iron elements 5 and 6 sothat thefiux threading the magnetic reeds of the device"8- be soreducedthat the reeds will returnto their normal position in which thecircuittherethrough is opened.

The'dial 3- operates a castellated armature 4 also of soft iron or otherlow reluctance magnetic material; In the position shown the air gapsbetween the-lower ends of the soft iron pieces 5 and 6 and the spokes ofthe castellated armature 4 areso great that the field of the permanentmagnet l-is not sufficiently affected by the armature 4 to release thecontacts of the device 8. Upon rotation of the dial, however. the spokesof the castellated armature 4 will periodically sufficiently shunt themagnetic circuit so as to allow the contacts of the device 8 to open.With the handset of its cradle in the position shown the dial will beineffective as the soft iron armature 9 already sufficiently diverts thefield of the permanent magnet I to open thecontacts of the device 8.However, when the handset is removed from the cradle 2 and the air gapbetween the armature 9 and the pieces 5 and 6 has become so great thatthe magnetic circuit is not affected thereby, then the movement of thecastellated armature 4 becomes efi'ective. Therefore, during therotation of the dial 3 and the coincident movement of the castellatedarmature 4 the contacts in the device 8 areperiodically opened andclosed and will perform the same functions as the contacts on anordinary dial.

' It will be understood that some means such as a one-way slip clutch orratchet for insuring that the castellated armature 4 will affect themagnetic circuit only during the return movement of the dial 3 will beprovided but since specific means of this nature are not part of thepresent invention, they will not be illustrated and described herein.

Fig. 2 shows an alternative arrangement in which the dial only affectsthe contacts. Herein a pair of soft iron elements I!) and I l correspondto the soft iron elements 5 and 6 of Fig. 1. A magnetically operatedcontact device I2 is shown at one extremity of the soft iron elements l0and l l and the castellated armature 4 is shown as associated with theother extremities of these elements'. The permanent magnet is placedpartway between the extremities of the soft iron pieces l0 and II. Inthe position shown the field of the magnet 1 will thread the magneticelements of the contact device l2 in sufficient force to close thecircuit controlled thereby. Upon the operation of the dial the spokes ofthe castellated armature 4 will periodically shunt the magnetic circuitand sufiiciently divert the field of the permanent magnet 1 from thecontact device l2 to allow the contacts therein to open and thus thecontacts of the device l2 will operate in the same manner as theordinary contacts of a dial.

It will be observed that instead of a castellated armature with aseparate pair of poles for each dial unit, an armature with a fewernumber of poles (two, for example) can be made to serve the same purposewith the intervention of a suitable ratio gear drive between the dialand the armature. By especially shaped armatures any arbitrary train ofcontact operations may be set up instead of simple trains of equalpulses.

By way of example, an impulse transmitter like that shown in Patent1,306,054 granted June 10, 1919 to J. C. Field may be constructed usingthe present magnetic switching principle. A transmitter of this natureuseful in an indicating system such as that shown in Patent 1,709,067,granted April 16, 1929, to J. C. Field may be constructed. In Figs. 3and 4 such a transmitter is shown. In these figures a handle I3 is usedto operate the transmitter. Through a suitable train of gears I 4 anarmature l5 may be caused to move past the pole-pieces l6 and I1. If thespokes l8 and I9, for instance, come into operative relation with thepole-pieces I6 and I1, respectively, the field of the permanent magnet20 is sufficiently diverted from the contact device 2| to allow thecircuit normally made between the reeds 22 and 23 to be opened.

It will be noted that the spoke i9 is small in dimension, that the spoke24 is larger and that the spoke 25 is still larger. That means that theopen circuit period produced when the spoke l3 is in operative relationwith the pole-piece I! will be of short duration, that the conditionproduced by the spoke 24 will be of longer duration and that thecondition produced by the spoke 25 will be of still longer duration.

It will also be obvious that a device of this nature need notnecessarily be controlled by an operator but may be controlled by themovement of some piece of machinery such, for instance, as the movementof a railroad semaphore for the purpose of sending answer-back signals.

Other uses for the signal transmitter of the present invention workingon the magnetic switching principle will occur to those skilled in theart.

What is claimed is:

1. ,In communication apparatus, a supporting structure, soundtranslating apparatus removably supported thereon, a magnetic circuit insaid supporting structure including a source of magnetomotive force,magnetically operated circuit contacts normally operated by said sourceof magnetomotive force and means for sufficiently diverting the fieldfrom said contacts to cause their release, said means consisting of aspoked memher for mechanically and repeatedly interposing a path of lowreluctance in said magnetic circuit.

2. In communication apparatus, a supporting structure, sound translatingapparatus removably supported thereon, a magnetic circuit in saidsupporting structure including a source of magnetomotive force,magnetically operated circuit contacts normally operated by said sourceof magnetomotive force and a plurality of low reluctance elements forinterposition in said circuit for sufi'iciently diverting the field fromsaid contacts to cause their release, one of said elements beingmechanically controlled to repeatedly affect said circuit, and anotherof said elements being carried. by said sound translating apparatus andpositioned therein to afiect said circuit when said sound translatingapparatus is in its normal position on said supporting structure.

3. In communication apparatus, a supporting structure, sound translatingapparatus removably supported thereon, a magnetic circuit in saidsupporting structure including a source of magnetomotive force,magnetically operated circuit contacts normally operated by said sourceof magnetomotive force and a plurality of low reluctance elements forinterposition in said circuit for sufficiently diverting the field fromsaid contacts to cause their release, one of said elements beingmechanically controlled to repeatedly affect said circuit, and anotherof said elements being carried by said sound translating apparatus andpositioned therein to affect said circuit when said sound translatingapparatus is in its normal position on said supporting structure, saidmagnetic circuit being constructed and arranged to render said firstelement inefiective when said second element is effectively interposedin said circuit.

4. In communication apparatus, a supporting structure, sound translatingapparatus removably supported thereon, a magnetic circuit located partlyin said sound translating apparatus and partly in said supportingstructure, said magnetic circuit including permanent magnetic and softiron elements and magnetically operated circuit contacts, said contactsbeing operated by said permanent magnetic element, said part of saidmagnetic circuit in said sound translating apparatus acting when saidsound translating apparatus is resting on said support to sufiicientlydivert the field of said permanent magnet from said contacts to allowthem to release and another element of said magnetic circuit beingarranged to operate mechanically to periodically sufficiently divert thefield of said permanent magnet from said contacts to allow them torelease.

5. In communication apparatus, a supporting structure, sound translatingapparatus removably supported thereon, a magnetic circuit located partlyin said sound translating apparatus and partly in said supportingstructure, said magnetic circuit including permanent magnetic and softiron elements and magnetically operated circuit contacts, said contactsbeing operated by said permanent magnetic element, said part of saidmagnetic circuit in said sound translating apparatus acting when saidsound translating apparatus is restin on said support to sufiicientlydivert the field of said permanent magnet from said contacts to allowthem to release, and another element of said magnetic circuit being inthe form of a spoked member rotatably mounted and controlledmechanically by a signal device, said spoked member in certain positionsthereof acting to complete a branch of said magnetic circuit tosufiiciently divert the field of said permanent magnet from saidcontacts to allow said contacts to release and in alternate positionsthereof acting to open said branch of said magnetic circuit to allow thefield of said permanent magnet to operate said contacts.

6. In combination, a telephone including a handset and a cradletherefor, a dial mounted on said cradle, a set of magnetically operatedcircuit contacts, magnetic means in said handset to operate saidcontacts and magnetic means controlled by said dial to operate saidcontacts.

7. In combination, a telephone including a handset and a cradletherefor, a dial mounted on said cradle, a set of magnetically operatedcircuit contacts, magnetic means in said handset to operate saidcontacts, magnetic means controlled by said dial to operate saidcontacts and means whereby said dial is rendered inefiective while saidhandset is resting on said cradle.

8. In communication apparatus, a dial for sending trains of impulsescomprising sealed contacts, a magnetic circuit insensitive to externalmagnetic influence for working said contacts consisting of an inductortype relay structure and a spoked member controlled by said dial forchanging the reluctance relations of said inductor type relay structure.

9. In communication apparatus, a magnetic circuit insensitive toexternal magnetic influence consisting of an inductor type relaystructure, a set of scaled contacts controlled by said magneticstructure, a dial, a spoked member for controlling said magneticstructure to operate said contacts to send trains of impulses, atelephone handset, and a magnetic element in said handset to alsocontrol said magnetic structure to operate said contacts in accordancewith the movement of said handset to and from its normal position.

10. A contact control device consistin of a magnetic circuit including asource of magnetomotive force, magnetically operated circuit contactsnormally operated by said source of mag netomotive force and means forsufficiently diverting the field from said contacts to cause theirrelease, said means consisting of a mechanically movable elementpermanently associated with and mounted in cooperative relationship withthe said other elements of said magnetic circuit for repeatedlyinterposing a path of low reluctance in said magnetic circuit forcreating a corresponding train of impulses, said mechanically movableelement being arranged and adjusted to interpose a path of lowreluctance in said magnetic circuit at a rate in the order of ten totwenty times per second.

ROBERT C. MATHE'S.

